Truants only purpose and information on it is that every two turns the pokemon will not do anything but what dragon arbock said is valid. Truant is a useless ability and should never of existed it only causes pain on good pokemon such as slaking.

ikey123 wrote:I know this is a bit late but can duarant use skill swap if so you could make it so your opponents Pokemon can only attack every other turn

It can't skill swap, but it can learn entrainment, which just replaces the other pokémon's abillity with Truant, but it still keeps the Durant's abillity Truant. The effect disappears when the poké switches out, though :/